In early electronic products, integration of multiple semiconductors with the same or different functions is to individually package different semiconductor chips and then SMT on a same printed circuit board. However, this kind of integration takes up larger footprint and space on a printed circuit board and can not meet the requirements of thin, light, and small. Therefore, Multi-Chip Package (MCP) was developed to integrate a plurality of chips in a same package, especially for memory products or portable electronic products.
Chips with different functions and characterizations are successfully integrated and packaged in a conventional MCP, however, the selection of packaging materials and processes have to be compromised to reach a balance point between different chips which may not be optimized.
A cross-section of a conventional MCP device is shown in FIG. 1 and its corresponding packaging process flow in FIG. 2. The components of the MCP device of FIG. 1 are described in sequence of the packaging processes of FIG. 2. The MCP device comprises a plurality of chips with different functions such as a memory chip 130 and a controller chip 140, a substrate 110, and an encapsulant 150. A substrate 110 is provided in step 11. In a first die-bonding step 12, a memory chip 130 is disposed on the substrate 110 through heating and curing the die-attaching material disposed under the memory chip 130. In a second die-bonding step 13, a controller chip 140 is also disposed on the substrate 110 through heating and curing the die-attaching material disposed under the controller chip 140 where the substrate 110 experiences multiple heating processes. In a first wire-bonding step 14, a plurality of first bonding wires 132 are formed through wire bonding processes to electrically connect the memory chip 130 to the substrate 110. In a second wire-bonding step 15, a plurality of second bonding wires 142 are formed by wire bonding processes to electrically connect the controller chip 140 to the substrate 110. Since one ends of the first and second bonding wires 132 and 142 are all bonded on the substrate 110 so that all the wire bonding processes can be done on the same wire bonder to avoid multiple loading and unloading to achieve higher throughput with lower operation cost, therefore, the materials and the diameters of bonding wires as well as the wire bonding parameters are the same. However, if chips without bonding wires are also integrated in the MCP device, then additional heating processes would be needed such as thermal bonding processes of flip-chip assembly and reflow processes of solder balls. Then, in an encapsulating step 16, an encapsulant 150 is formed on the substrate 110 through molding processes to encapsulate the memory chip 130 and the controller chip 140. Finally, in a package-singulating step 17, the substrate 110 and the encapsulant 150 are cut through the scribe lines to form a plurality of individual MCP devices. Therefore, the processes, materials, and processing parameters of the existing packaging processes for MCP using the same substrate to carry a plurality of chips with different functions can not be optimized according to the specific functions of each individual chip. Moreover, as more chips are stacked in a conventional MCP device, the substrate would experience multiple heating processes which causes uncontrollable package warpage leading to more package processing issues.